Rotary refiner



March 17, 1953 E. P. ARPIN, JR., ETAL ROTARY REFINER 3 Sheets-Sheet 1 Filed July 7. 194s March 17, 1953 E. P. ARPIN, JR., ET Ax. 2,631,504

ROTARY REFINER Filed July A7, 1948 s sheets-sheet 2 a v a Tyan/Zar' l EdmzzzzdPHQQzm/f:

Eazymozzdlye 1%/ L March 17, 1953 E. P. A RPIN, JR... ETAL ROTARY REFINER s sheets-sheet s Filed July 7. 1948 Patented Mar. 17, 1953 .T 'fo STATE-,s PATENT oit-Fics .Edmuni1`1?.Arpin,..Jr., Neenah, Wis., and Ray- -mond'PElJyQ Chicago, 111;.; said Frye'assignor ,l inventdnntelatesi toiimprovementsin :rofi'tatytreiining'zmaehines wh-iehfare eised l:to trene wel?. DbrOi-.ls ..material,; suehas pulp, paper stock eandlthe like. fMoreJpartieularlythe presentan- Yentijon has to do ifwith .-irnprowements in rotor :bers assures a niniform iappli'cation of pressure tenian-aparts 'ofst-hefzrotorsstoneaathutminimizing the possibility of stone rupture or uneven'avearinglotithestonesurtace.

wide'dbetweenfdshe#surfaceof-@the'frotar-element fandf thessurf-aee ofithefabrasiveiiningiothezshell -hyfmeansr: f "vasimple leverlrfulcrumed l.insai-*l-illow box-like housing secured to the central'fholi-1owsshaft=ffthei-otor;renerhavingmnerenddis :posedfin an aperture=iin1an pstandingeearf portiomA fithel backinglfplatemndlftheeother fend 4arffxfangedfforleontaet with a;radially*=exten`dingspin Wh-ienentends`=irltothe interiorfdffa hollow shaft which :constitutes the rfrotor @shaft Lwedge'f-like members fmovable K:within ithe 4hollow shaft are L'externaliysopesabletorfforce 'thearadiallyextend- '.'yingfpin-sf outxxl-arfdlyl andithus Srl-imt the .amountfof :minimum iclearanee vmov/iden between the ccoonenatin'gfsurfacescf thermton elementfand ithe :abrasiveflining ontheshell.

:116111` #novel :r'eonstruetion :further provides sa fthreadefd .2 clamping member :assoeiated iwiththe .llongitudinal tro'd -f connected `@to v4the we'dgeelike I.members 'Sfor fzadjusting each :rod longitudinally f2 Yclamping .un-its ...are vassemblevjl `land thus 'simul- .-,taneously ...adjust all the rods "longitudinally `-in tlie.hol-low. shaft. :Thecalibrated 'dial-method of v-individually adjusting ...each rod, and ftherefore .each setbf (rotors, in 'the vhollow .sha t, is :obviously :a ,great ...advantage v.since Van accurate record Wof .'the.,clearanceslbetween 'the rotor `stone and'the abrasiueflining can'loe kept 4withoutchecking' the zclearancepitself Iby opening 11.10 the casing `oftl'ie ,1P ...notarygrening machine. K The provisionforgad- .iusting .allof the individual .adjusting mecha- 'nis1n5as. a .unit .provides a means whereby 'after .an Noriginal .adjustment of Ltherotor clearances, .subsequent adjustments.mayjibeiquickly andanll5 `eurate'ly made by moving .the .entire unit.

"Itis .therefore animpontant object rof `thepres 1 ent invention yto l.provide a .mounting for a 're- ,ning. element in .arotary renenassembly Which maybe quickly and easily Vvremoved Afrom .orin- `-20,..serted into the backing ,plate ofjthe rotor assembly .without .disturbing adjacent ,rotori assemblies .and .whichrproizicles means vfor quickly andeasily .adjustingthe rotorinplace.

A further object of this'inventionjis`.toprovide .25 ...a.rotor,rener. comprising. astationary shellhav- `inge. cylindrical ,.abrasiuelliner and .a rotQrin- .,cluding .centrifugally acting .rotor elementsihaving abrasive .surface for .cooperation .with 'fthe .abrasiwelining -to bring .about .the desired. renf.\A minimurmoperating videarance;isasilvvaysipro- 5-..30 :ing F.ation .and .wherein an `efrternally .operable ,.elampingnevice:carrying.calibrated..meansisas- .soeiated with ,an .internal .lever mehanismlfQ'r .accurately adjusting ltl'ieminimum vclearan@ebelftween the associatedorotor.elements-.andtheabra- Itjis a further important .Object Yof Lthisinten- ,tion to, provide. a rotaryrener. comprising wedgelikefmembelfs.movable.Within ahllowshaft, .each wedge-like member ,being .arranged toadjustthe 40 clearance between .af set ,0f Vassociated rotor ele- G45 `teriornf themachine.

@ther .and afurther important @objects ...of ...this :invention .fw-i211 be-fajpparentrom .the disclosures .ginfthe specieationeand.the-accompanying drawimg On the drawing: Y

e-Eigure l.1 isa-longitudinal elevationaleyiew of sanitary renner; embodyingtlie .principles of-iour i:nvention;with.parts; broken: atyayzand; inifsection. andzwithcothermarts inaelevat-io asia n umtgthe plgfnrmion lwhih 11 sehe .155 zFigureiZ is .-a fragmentary V:verticaal :sectional view taken substantially on the line l1-II of Fig. 1 with parts in elevation.

Figure 3 is a fragmentary vertical sectional view taken substantially on line III- III of Fig. 2.

Figure 4 is an elevational view of the end of the rotary renner of the present invention wherein the novel unitary adjusting means of this invention is disclosed.

Figure 5 is a fragmentary vertical sectional view taken substantially on line V-V of Fig. 1.

Figure 6 is a fragmentary horizontal sectional view taken substantially on line VI-VI of Figure 4.

Figure 1 is a fragmentary enlarged sectional view of a portion of the adjustment mechanism shown in Fig. 1.

Figure 8 is a fragmentary vertical sectional view taken on line VIII-VIII of Figure 4.

In Fig. 1, the reference numeral I indicates generally a rotary rener embodying the principles of our invention, including a generally cylindrical shell or casing II defining a support structure which is supported normally in horizontal condition upon suitable supports I2. The shell II is provided with end plates I3 and I4, the end plate I3 at the inlet end of the machine and having an inlet opening i5, and the plate i4 at the discharge end having a discharge opening I6. Each end plate is outwardly dished and provided with a central boss I8 defining a central opening for receiving, in bearing relation, a hollow shaft I9. Said shaft I9 is adapted to be rotated centrally in the casing II by a grooved pulley 29. Disposed within the dished portion of the inlet end plate I3 and secured to the shaft is an impeller member 2l which receives the material as it enters the inlet opening I and directs it toward its periphery for subsequent passage between the working surfaces of the refining machine.

The shell I I is provided internally with a liner 22, composed of a number of ring sections 23 which are formed of suitable abrasive material, such as stone, metal or a synthetic ceramic of an abrasive type.

As best seen in Fig. 2, a series of equally spaced helical grooves 24 extend longitudinally in the lmachine and form continuous passages along the inner surface of the ring sections 23.

The particular refining machine herein illustrated to disclose the novel rotor construction and mounting of the present invention includes rotor assemblies 25 pivotally mounted on a housing 29, in peripheral sets of four each, for rotation with the hollow shaft I9 to which a tubular central portion 33 is keyed. Each rotor assembly includes a rening element 21 secured in a backing plate 28 which has spaced upstanding ear portions 3I, Fig. 3, which straddle flange parts 32 on the housing 29 and are pivotally mounted thereon by a pin 3D. As the shaft I9 is rotated, the rotor moves outwardly by centrifugal force causing the refining element to coact with the abrasive surface of the liner ring 23 to refine the brous material as it is moved between the reiining surfaces by the action of the impeller 2I and by the pressure head under which the material is delivered to the inlet opening. Both the liner ring 23 and the rotor element 21 may be formed of stone, metal or of asynthetic ceramic of an abrasive type.

A feature of the present invention is the provision of a simple, positive acting linkage for maintaining a minimum clearance at all times between the surface of the refining element and the abrasive surface of the liner ring 23. This linkage ting contact with the end of a push rod 42 slidably mounted in aligned radial apertures in the hollow shaft I9 in the housing 29.

As a means of controlling the radially inward and outward movement of the push rods 42 there is provided a series of frusto-conical wedge members 43, Fig. 1, secured to telescoping rods 44, 45 and 46 extending longitudinally inside the shaft I9. It will be noted in Fig. 1 that two wedge members 43 are secured to each rod. The position of each of the rods 44, 45 and 46 may be adjusted individually or they may be adjusted as a unit from the outside of the casing by means Which will be described in detail hereinafter.

The inner end of each push rod 42 is in contact with the face of one of the wedge members 43 and, thus, the longitudinal positions in the shaft I9 of the members 42 determine the extent of outward pivoting of the rotor assemblies 25. A spring 48, Fig. 2, is disposed about the hub portion 36 of the rod 35 having end portions 49 resiliently urged into contact with the tubular portion 33 of the housing 29 and a roller equipped end portion 59 in contact with the face of the backing plate 28. This spring 48 prevents the rotor stone assembly 25 from dropping away from the ring 23 when the machine is shut down.

Further details of construction and operating of a rening machine to which our novel rotor constructionV and actuating means may be applied, may be had by reference to the copending application of one of us, Edmund P. Arpin, Jr., U. S. Serial No. 640,734, filed January 12, 1946, now issued as Patent No. 2,475,869,

Referring to Fig. 2, the backing plate 28 comprises a substantially at central portion 52 with an overhanging ledge 53 which extends across the trailing end of the plate forming a heel against which the corresponding portion of the stone 21 is pressed when the rotor is assembled therein.

At both sides of the backing plate, a wall portion55, Fig. 3, extends away from the ilat central portion 52 to provide a recessed chamber 56 which is adapted to receive, in guiding relation, a strip 51 formed on the stone 21 to t in the chamber.

An important feature of this invention is the provision of a novel means of securing the rotor stone 21 in `the backing plate 28. As shown in Fig. 2, a metal pressure pad 59 is disposed across the leading edge of the rotor stone with a pad of cushioning material 60 between the surfaces of the pad 59 and the stone. This cushioning pad 60, which may be made of a material such as rubber, soft metal alloy or plastic, protects the stone surface under compression against metal surfaces. In this connection, a cushioning pad 6I, Fig. 3, may be disposed between the rotor stone strip 51 and the backing plate 52 and also between the metal housing II and the various ring sections 23 which form the abrasive lining.

A series of wedges 62 are disposed between an overhanging ledge 63 at the leading edge of the backing plate 28 and the pressure pads 59. A stud bolt 65 is threaded at one end into each backing plate 28 and at the other end passes freely through an opening in each wedge 62 for :ana-irene thzea'dedfengagement evvthaf-mut1?!. i'rByi-tightvreningithe' nut 61 Wfrachrwedge--I2 "may lbei forced inwardly `to press `vthe :pressure Ajpad-iii) nagainst the frotor stone Vand firmly-urge iti-into vplace 1in the backing-platef.

"It'is Vtiriereiore "seen Vthatithere'isfprovide'd 2in this invention a novel wedge 'means for adjustably securing a rotorffstonein-@a backingi-plate.

outer-'periphery yof @the 1vrotor 'each reningiele- -m-entmaybe remove'di'from lorffinserte'dsiintotl-ie backing jplate aiiithoi-it disturbing rthe adjacent rotor-assemblies inf the reningmachine. 21-Fur 'then'the pressure-:pad 59 -f-Wliich-r-aextends#across :44,1115zandidfrespectively. fEachl-ofzthesecciarnparyitable-likerame;member 1.1,'Xedi-ygattached `as a part f of thessupportistructurecshell 'lrl :on Whichtheplatformisislidably disposed. Onefside of Lthezcollar '13 lissropemqiroviding rabuttingz ,arms .1-8 and 2TH Wl'lich :may :bie --drawn i-tQgether Aby boltsf.

vi In -Fig .1":8 :itiis ascent-that; ,thezclamping :assembly 10 :also Acomprises a threaded-'.-body .member l1,82 on @which smay .-beintegrally lfiormed `torfsuitably secured the rod 44. ,Thesgcollar f- 1,3 internally threaded tozreceive 'fat-he .ibodyzmember 118-2 which `has;afiiangednnd:portionSrarrangedrtoabut,,one endzzofztheicollar E13 -to limit:longitudinalsmovement of-:the threaded fbodyimember- :82. A -series of :holes :85 :aregprovided v-inthe periphery fof the iendnportion -83 .into Iwhich :a: bar -83a `may-.he in- :serted for;rotating.the-member. 82 ymathe stationaryzzcollar and thus imovingthe member :82,

v;.1'.he:,connected .-rod A4 -and the associated ,coneyshaped wedges ,-43 longitudinallyin `the `hollow .shaft ,fl-9. It will ,be fund-erstood, 1, of bourse, ,that Whenfanfadjustmentfis v.being-made, .the `l bolts. 80 will .-.be :threaded .outwardly Tin vthe arms 18 `and *1,9 Ltorelax .itheggrip-.of thecollar J3 .on .thelbody ,member 82.

In order to coordinate the ,-settings 4,or '.the VWedges .43 ,i in the ishaft 1l 9, a .calibrated ',.arm T86, Eigurel isesecured tothe-uppeixsurface .off reach collarassemblmzextending :axially of .the.threa d ed body.;,member, 82 .with a free end portion., ,86a -overhangng a calibrated .ring 81 rotatably mounted on; an...annular;shoulder.88 .of Lthe A,body member82. .Aplurality of cap ,screws "8.9 are Lthreaded into ,the `member 82 against a washer *I B0-.which overlapsrtheedge .oflzthe calibrated'ring ,The arm 1316 Vmaybeicalibrated so'that Wone-"full y,re'volutiongof the member',82 `Will'causeithe iongitudinal .movement 'gthereof a distance equal "to one Cdivisionmark on the arm. The `ring :'81 "may fhe-,calibratediinany suitablegpart `ofarrevolution, as ,for example eight #divisional parts, Aas shown ;iriEig.;5. I

j, Each of the clamping assemblies "'10 ,"-l :and "q-Z are identical 1,except "for Mthe @provision 'in vthe threaded body'member of --thefassem'biy Jl-2 for free flongitudinal passage therethrough of rods T41 an'd 15 .andzthe 1provision *in passenriblyH for "75 6 (free-longitudinalfpassagetherethroughof'frodll ;The-'-threads inthe-body memberof=each-assem blyhave identical pitches-s0! thatcequal-rotation of :each -member :will --fcause equal longitudinal movementof r-lthe associated yrod in "the hollow shaft 14). Thus, in Fig; 8, if,thellange'd Send-83 is a position i for :abutting the @collar '13, i. the edge-6811i fof the `Aring 81 isl aligned fWith theirst 'division mark, v:indicated by vre'ference numeral '93, onithefV armfandltheizero1mark,-1Fig.i5,1 on :the *face v'o'--the 1-ringi-'I `isf-aligned:radially with the vedgeof..-thenialibrated.:arrnlt. Subsequentsrotation fof the'bodyr-member 88 away frornithev initial :,settingzwillthen be yrecorded by Vthelongitudinal andrradial movement of'sthe :ring 81.

`nsf-previouslymentioned, eachl 4of l theco'llarseof fthe xthree f-clamping assemblies is '-:secure'd Lto'a platform' i5, which iis slidably `mounted ron va stationary base 11. This :platform can f-be zse- .cui-edito the -fbase .Tl :by drawinga l:longitudinal `stripill'l up .tightly Aagainstfthe rlower surfaces 'ifa of-the-lbase '1? 'and"5'l5a `of :the: platform 5:15 :which are disposed in flush relation at either sided-of the-base 1:1,

'f-It -is -a/special feature fof *this invention ithat lthe-1'olatform 115 Vcani-be- *adjusted' bodily. relative `vtothe-frame for simultaneously adjusting allzthe rods -SQdA-E-and i'fmountedthereon. 'iT-his ais accomplished -fby :means of 1.a .disk'i-SS Adisposed :in an aperture-9 'l of fasubstantially:rectangular cor-ifigur-ation on'ethel platform Tel-5. The-.diskle issec- `Acentrically securedvto 'the endrofaa .rodfizwhich is fjournalledifor-rotation inl a passage Siiiextend-` ing downwardly through vadepending arm rl of 'the platform .71. The :lower fend :of the rod 1J 8` issecured,-asbywafpinI1l2,:tofa rotatable .socket member il il'f-Which'ihasza `slot"I l Mtadaptedto receive a bar lfi5 vforrotating-the eccentric disk. AIt Will be apparent Ffrom rligs.ffand .fzthat rotation ofthe 'disk will vcause reciprocating@longitudinal movement of the `Vplatform i5 .an-dithev clamping assemblies-mounted thereon.

-'-From theforegoing :description it is seen that "there-is` provided in this inventioninovehthreaded means ffor separately adjusting leach rod longitudinally ofthe lhollow shaftiil 9,r andan leccentric meansI f orfad-j usting i all'srodsdn .the rotaryirener simultaneously. vEach-of .thesemethods @fadv-j ustmentrepresents.,ardistinctI advance in the .art since they afford v-for theiirst time -.means for accurately adjustingmotor .clearanoe,` ffoLkeeping a recordoflthe clearanceioanyione setiofzrotors :an'd'for comparing'at aglancethekclearances of allisetsoffrotors.

'-'It will, of c-ourse, be understoodLthat various details of construction -imay ,be ,varied :through :a Wide range l.Without Ydeparting Afrom the ,principles "of Vthe presentinvention, and it is,.therefore, not .the purpose to limit the :patent :granted Y hereon otherwisethan .necessitated by the-scope of lthe appended .-claims.

-1. -Ina rotary'rener fori-wet fibrous material,

a -rotor assembly --comprising a backing vplate including `-a V`'recessed portion defined by marginal flanges 'and having `threaded :passageway/fs fad- -jacent the-leadingedge ther-cof,v a stone `refining element movable into -said recessed Yportion `against 7sa-id flanges having a generally arcuate vprocessing :surface and a vhat -surface extending acrossthe` leading edgeya pressure pad positioned against "said at surface, f a 'plurality of Vwedge members disposed f-betweensaidI pressure-:paduiand fafange l0f saijd ybacking plate iand having pas :sageways therethrough fin valignment :with V:the

passageways in said backing plate, threaded studs projecting through the passageways in said wedges for engagement in the threaded passageways of said backing plate, and nuts on said studs for exerting pressure on said wedge members.

2. In a rotary refiner for Wet brous material, a stationary shell having a cylindrical abrasive liner, a hollow drive shaft, centrifugally acting rotor elements movable against said abrasive liner, members secured to said shaft, pins carried by said members for pivotally mounting the leading portions of said rotor elements, levers pivotally mounted intermediate their ends on said members and having free end portions, rods associated with one end of each lever and extending radially through said hollow shaft, an arm portion projecting from each of said elements and having an aperture for receiving the other end of each of said levers, and wedge means in said hollow shaft associated with the radially inward end of each rod for controlling the amount of clearance between said rotor and said cylindrical shell.

3. In a rotary rener including a support structure, a hollow shaft rotatable in said structure and secured against longitudinal movement relative thereto and a plurality of telescoping rotor-adjusting rods movable longitudinally of said shaft, apparatus for simultaneously adjusting all of said rods longitudinally in said shaft comprising a platform having a slot therein and being slidably mounted on said support structure, threaded collar members secured on said platform, a threaded member secured to each rod and in threaded engagement with one of said collars and eccentric means journaled in said support structure and engageable in the slot in said platform for shifting said platform longitudinally of said shaft.

4. In a rotary refiner including a support structure, a hollow shaft rotatable in said structure and secured against longitudinal movement relative thereto and a plurality of telescoping rotor-adjusting rods movable longitudinally in said shaft having threaded end portions extending out of said shaft, apparatus for adjusting all of said rods simultaneously longitudinally in said shaft comprising a platform slidably mounted on said support structure, and threaded collar members secured on said platform, one of said collars being in threaded engagement with the end portions of each rod.

5. In a rotary refiner including a support structure, a stationary shell having a cylindrical abrasive liner, a hollow shaft rotatable in said structure and secured against longitudinal movement relative thereto, centrifugally acting rotors movable against said abrasive liner, flanges extending radially outwardly from said hollow shaft, pins carried by said anges for `pivotally mounting the leading portions of said rotors, levers pivotally mounted intermediate their ends on said flanges and having free end portions, rods associated with one end of each lever and extending radially through said hollow shaft, an arm portion projecting from each of said rotors and having an aperture for receiving in positive abutting relations with one wall thereof the other end of each said levers, wedge means in said hollow shaft associated with the radially inward end of said rod for controlling the amount of clearance between said rotor and said abrasive liner, a rotor-adjusting rod connected to said wedge means and having a threaded end and movable longitudinally in said hollow shaft,

and 'means for adjusting said rod in said shaft for actuating said wedge means to control the clearance between the rotors and the abrasive liner including a threaded collar mounted on the support structure for engagement with the threaded end portion of said rod and means for rotating said threaded portion to move said rod longitudinally in said shaft.

6. In a rotary refiner including a. support structure, a hollow shaft rotatable in said struc. ture and a plurality of telescoping rods movable longitudinally Yof said shaft, apparatus for simultaneously adjusting all of said rods longitudinally in said shaft comprising a platform slidably mounted on said support structure, threaded collar members secured on said platform, a threaded member secured to each rod and in threaded engagement with one of said collars,

and means journaled in said support structure and engageable with said platform for shifting said platform longitudinally of said shaft.

7. In a rotary refiner for wet fibrous material including a support structure, a stationary shell having a cylindrical abrasive liner, a hollow shaft rotatable in said structure, centrifugally acting rotors movable against said liner, flanges on said hollow shaft, pins carried by said flanges for pivotally mounting the leading portions of said rotors, levers pivotally mounted intermediate their ends on said flanges and having free end portions, rods associated with one end of each of said levers and extending radially vthrough said hollow shaft, means on each of said rotors engaging the other end of each ofV said levers, wedge means in said hollow shaft associated with the radially inward end of each of said rods for controlling the amount of clearance between the corresponding rotor and said abrasive liner, a rotor-adjusting rod movable longitudinally in said hollow shaft and connected to said wedge means and having a threaded end, and a fixed threaded collar cooperating with said threaded end for ajusting said rod in said shaft and thus actuating said wedge means.

8. A rotary refner comprising a support structure, a hollow shaft rotatable in said structure, a plurality of telescoping adjusting rods movable longitudinally in said shaft having end portions extending out of said shaft, means cooperating with said end portions for adjusting Veach rod in saidshaft independently of said other rods, and Vapparatus for simultaneously adjusting al1 of said rods, said apparatus including a platform slidably mounted on said support structure and means carried by said support structure for moving said platform.

9. In a rotary refiner for wet fibrous material, a rotor assembly comprising a backing plate including a recessed portion defined by marginal fianges and having a leading edge and a trailing edge, said backing plate having a threaded passageway adjacent one of said edges, a stone refining element disposed insaid recessed portion and seated against one of said l'marginal flanges and having a generally arcuateprocessing surface and a flat surface extending across said one edge, a pressure pad positioned against 'said flat surface, a plurality of wedge membersdisposed between said pressure .pad and the other marginal flange of said backing plate and having passageways therethrough in alignment with the passageways in said backing plate,

.threaded studs projecting through the passageways in said wedges and eng-aged in the thread- .ed passageways of said backing plate, and nuts 9 on said studs for exerting pressure on said wedge members.

10. In a rotary rener for Wet fibrous material, a stationary shell having a cylindrical abrasive liner, a drive shaft, oentrifugally acting rotor elements movable against said. abrasive liner, members secured to said shaft, pins carried by said members for pivot/ally mounting the leading portions of said rotor elements, levers pivotally mounted intermediate the ends thereof on said members and having free end por tions, an arm portion projecting from each of said elements and having means for receiving one end of each of said levers, and means operatively associated With the other end of each lever for effecting pivotal movement of the lever to control the amount of clearance between said rotor and said cylindrical shell.

l1. A rotary rener comprising a support structure, a hollow shaft rotatable in said structure, a plurality of telescoping adjusting rods movable longitudinally in said shaft having end portions extending out of said shaft, means cooperating with said end portions for adjusting each rod in said shaft independently of the other of said rods, apparatus for simultaneously adjusting all of said rods longitudinally in said shaft comprising a platform having a slot therein, said :platform being slidably mounted on said support structure, threaded icollar members secured on said platform, a threaded member secured to each rod and in threaded engagement with one of said collars, and eccentric means journaled in said support structure and engageable in the slot in said platform for shifting said platform longitudinally of said shaft.

EDMUND P. ARPIN, J R. RAYMOND P. FRYE.

REFERENCES CITED The following references are of record in the file of this partent:

UNITED STATES PATENTS 

